Thursday, September 11, 2014

test post

blah blah my offline blog client is busted

Tuesday, May 21, 2013

this isn't going to be easy...

Short version: I am "renouncing" all of my technical "mad science" hobbies, including anything involving high voltage, stored energy, high energy physics, etc.

I am already in the process of disposing of all the projects, parts, materials, and support equipment relating to same. I'll sell what I can, give away or throw away what I can't. Much of it is so large and heavy I would rather have it hauled away for scrap than deal with crates, skids, forklifts, flatbeds, or other heavy motor freight means.

This is not a joke, nor is it a decision I've made in haste. I have spent the first 50 years of my life completely scattered, unable to focus on or choose the things which matter to me most.

Now that I am on Ritalin (40 years too late, sigh) it has become quite a lot easier to prioritize -- to determine which hobbies I can do well, which ones are impractical to pursue, not to mention which pastimes will be the most gratifying.

I still have one or two hobbies remaining, but I desperately need fewer of them in toto.

As a result, this post could be the last I make to this blog, unless I feel a need to announce other unrelated future accomplishments to the world, such as semi-artistic creations. I would like to finish (and SELL) the "Mad Scientist's Light Switch", and I would like to finish the rolling ball sculpture I started a bunch of years ago.

I am hanging onto my shop and fabrication resources to use for the remaining hobbies.

I expect I'll just let this page sit here a while, and then eventually delete the blog completely.

Oh, and if you are or if you know anyone in the Denver / Front Range area in Colorado who is interested in high voltage, Tesla coils, railguns, pulsed power, etc, please put them in touch with me - I probably have something they want.

Monday, April 15, 2013

the ultimate shop vacuum?

I own a Shop-Vac "QSP" series shop vacuum. I bought it used from eBay (it was actually being sold by a pawn local shop, so I didn't have to have it shipped)

It has good suction power with a fresh filter, and unlike most shop vacuums I've used, it doesn't hurt my ears the way most shop vacuums do; the highest and most piercing frequencies have been muffled. This is good - many shop vacuums are loud enough and piercing enough to cause real hearing damage. I've seen units which owners have fitted with sound-containing housings around the blower motor. That's all that the makers of the newer, quieter units are doing - adding some plastic and a bit of foam rubber to absorb the high sounds while letting the air flow around corners in the muffler housing to get out. You can DIY that sort of thing if your unit is older and louder / more piercing.

My one complaint about my unit has been its poor air filtration and dust leakage, and the fact that most of the filters I had tried clogged up too quickly, killing suction too quickly. Until recently, every filter I tried either did not filter fines very well, or if it did, it clogged up and had to be cleaned frequently. More expensive, user-cleanable (not disposable) filters saved money, but cleaning them was incredibly messy and tedious.

Recently I discovered "drywall filter bags", intended to be used inside any typical shop vacuum. These are bags made from reinforced filter paper, not terribly different from the ones many household vacuum cleaners use, except that they are much bigger. This product was developed for cleaning up drywall dust during or after sanding, one of the messiest household (or contractor) cleanup jobs there is. Drywall dust clogs most shop vacuum filters very quickly. The bags have more surface area than any cylindrical filter could, they are fairly easy to put in and remove, and they completely contain very fine dust. They have a rubber gasket which fits over the intake port of the vacuum cleaner's tank to prevent dust-laden air from going around the filter bag.

Recently I also found a shop vacuum filter claiming to be a "HEPA" filter. "HEPA" is an acronym for High Efficiency Particulate Air, and it has a specific definition, at least in the USA. To qualify as HEPA grade, a filter must remove 99.97% of all particles larger than 0.3 microns (micro-meters, or millionths of a meter) from the air passing through it. That is a non-trivial task, and quite frankly, the vast majority of air filters being sold to consumers as "HEPA" grade filters do not actually qualify. Read the manufacturer's own claims of particulate removal and see if it matches the criteria above.

Even if these filters aren't true HEPA grade, they do a REALLY good job of removing very fine dust and allergens. So a few weeks ago, I dropped about $30 for a close-to-HEPA grade filter, and about $16 for three disposable drywall filter bags. The HEPA filter mounts on the vacuum motor lid in the usual manner, and the drywall bag wraps around that filter and extends below as well, filling the entire tank. Whatever the drywall bag doesn't catch, the "main" (now secondary) filter does, and airflow restriction is nearly nonexistent with this setup. When the bag is finally full (ie; when the suction finally starts to drop), you just pull out the bag leaving the tank completely clean.

The air coming out is clean enough not to trigger my or my wife's allergies - I can't even detect the faintest hint of dust.

Obviously this set-up is for dry vacuuming only. If you need to do wet vacuuming, you need to use the specific filter type intended for that job. I've yet to see a very good filter for wet vacuuming, most of them are simple foam sleeves.

PS: most regular cylindrical shop vacuum filter have a foam rubber gasket which should seal air- and dust-tight around its mounting position. I have found that if that plastic sealing surface or the gasket on the filter are not clean, fine dust can leak past. Wiping the dust from the sealing surface with a damp rag prevents that issue. Once you've started using the above setup, you won't see nearly as much dust collecting on those areas in the future.

Hope these tip help someone else.

Sunday, March 17, 2013

Tesla coil completion & "first light" tests

During the last week, I finished 'My Last Tesla Coil', at least insofar as it can be operated and is not an ugly mess to wire up. I was moved to push hard and get it working before Saturday March 23 (six days from today) which is the scheduled date for two grand opening parties for two businesses run by friends of mine.

The owner of The Concoctory wants the coil to be present and running as an attention-getter near the store.

Down the street and around the corner is a great little café called Cafe Crescendo, who are also opening that day. I gather that between them, they are trying to get the other local businesses to join in a sort of block party to draw attention further south to all of the existing and new businesses which are opening in that (newly renovated) south Broadway neighborhood.

Clever, fun, smart people are behind both operations and I hope I can add some sizzle and excitement to their opening day.

Yesterday, I set up the coil in the parking lot of Denhac, Denver's very own local hackerspace, and fired it up. After several extra trips to various places for forgotten parts and to put gas in the generator, and then perhaps fifteen minutes of the usual first-time tuning of the primary tap, adjusting the safety gaps in the power panel, and adjusting the main spark gap (an air-blast or "sucker" gap, the first of at least three gaps to be built for this coil) I obtained some reasonable results; approximately 36" streamers from the toroid.

I was expecting and hoping for closer to 60" streamers, however two problems rapidly became apparent during yesterday's tests:

1) the alleged "3,000 watt" generator (the only one readily available at no cost to me) is either failing to deliver its full rated power; or perhaps it is getting some RFI or spikes from the coil, causing its regulator to reduce the RPM; or -- and this seems the most likely cause to me -- the reactive load is causing a low power factor, resulting in more current being drawn from the generator than necessary and less "real power" being delivered to the load.

2) the spark gap was not quenching reliably (or at all). I don't have E/H field antennas for an oscilloscope which would confirm that theory, but I have enough experience with Tesla coils that I know a badly operating spark gap when I see and hear one. This gap (described here) uses an air blast to encourage the arc to extinguish (quenching the primary circuit) immediately after it has established. This is the desired "opening switch" operation of a spark gap, and it is much harder to achieve than the initial "closing switch" operation which precedes it in each firing cycle.

[aside: "opening switch" is a term of pulsed power jargon which refers to
switches -- there are a variety of methods -- which are designed to
interrupt current flowing in a circuit as quickly as possible. Opening
switches are frequently used to transfer energy between stages in a pulsed
power system.

A brief pulse of current is made to flow from a charged energy store having a
relatively long time constant into a following stage having a shorter time
constant, by way of passing electric current through an already-closed opening
switch. When most of the energy has been transferred into the next stage, the
switch is opened, causing the current to cease very abruptly. This "traps"
the transferred energy in the next stage, whether the energy is being stored
in an electric field (capacitance) or a magnetic field (inductance).

When the energy is again transferred out of this second, "faster" stage into
either another power amplification stage or the load, the smaller reactance of that stage causes the pulse to be delivered in a shorter time. Because the same amount of energy is now being transferred in a shorter period of time,
the peak power increases proportionately, obeying conservation of energy.]

While I have experimented with air blast gaps in the past, this gap was my first experience with the "sucker" design, which pulls air into holes in the electrodes, creating an axial shearing flow across the faces of the gap. While I was tuning up the coil, I noticed that the gap operation was not being affected much by the amount of air flow.

The gap did not work well at the original electrode spacing. With a conventional gap, if you want to increase the voltage at which the gap fires, you open the gap spacing. In a sucker gap, once the gap spacing exceeds the cross sectional area of the gas ports in the electrodes, the air speed across the faces drops dramatically, which spoils the quenching action.

The solution would seem to be opening the holes in the electrodes a bit (which I did after yesterday's test run) and reducing the gap distance, relying on the air flow to quench the gap rather than a long arc distance, which merely increases resistance in the gap and thus wastes power badly.

Some finessing may be required on one or both electrode faces as well.

The coil tuned up (the system resonates around 105 KHz) at 9 turns on the primary. I was shooting for 10 turns and there are 14 turns available, so that was agreeable. It would not hurt to have a slightly lower capacitance in the primary tank capacitor, which would allow (require) a few more turns on the primary. Counter-intuitively (because turns ratio in a Tesla coil doesn't matter as much as one might expect) increasing inductance in the primary tank circuit acts to reduce the peak current through the gap. Because gap losses increase as the square of the current, a small reduction in primary circulating current results in a large reduction in lost power. This improvement in efficiency completely swamps the small change in output which might otherwise result from reducing turns ratio.

So, before next weekend, I've got to find a slightly beefier generator. It's probably that some PFC capacitors on the line side of the HV transformer will reduce the amount of current being drawn from the 120V supply, but that's unlikely to happen in the next six days.

I also need a better-working spark gap. I have already modified the existing spark gap, but it will take a little experimentation before I can confirm whether the changes make enough of a difference.

It might actually be possible to build a Richard Quick -style multi-gap before next weekend, especially since I started work on one over a year ago; I have all the electrodes fabricated (but not yet drilled) and I probably have a suitable muffin fan in stock...

Wednesday, February 13, 2013

MLTC progress

I completed the HV section of the power cabinet for 'My Last Tesla Coil' last night. This morning I powered up the whole cabinet and verified that:

• no flashovers or evident leaks, no visible or audible corona at full volts

• full volts at both HV connector ports - no corona or leakage from HV rear panel connectors

• no breakdown problems with the RG-213 cable I'm using for HV leads between the power cabinet
and the coil

• the Terry Fritz filter section _appears_ be okay

In short, I wasn't really expecting everything to work fine the first time. There is no front panel on the power cabinet yet, so there is no way to control power to the HV transformer, but the coil is a LOT closer to First Light and tune-up testing than ever before.

There is an event in Denver at which this coil is wanted for a Grand Opening near the end of March. We'll see.

Monday, January 28, 2013

Tesla coil and "why so many projects?" also, "why don't you ever finish anything?"

1. Tesla coil
I am making headway on the Tesla coil, and have redoubled my efforts (in between trying to do real work for real money, about which more down below) because a friend is opening a very cool new art-nerd / techie arts & crafts type store in Denver, and very much wants to have an impressive Tesla coil at her grand opening in March, which is, um, roughly a month away. Oi. We'll see. I'm trying.

2. "Why do you have so many (unfinished) projects?"
I suffer from ADD - Attention Deficit Disorder, and have my entire life. It's been marginally worse since I had a protracted fever a few years ago. I now take Ritalin, and it has changed -- or I should say 'is changing' -- my life. Sadly, that's 45 years too late, but better late than never.

In the past, whenever I hit a snag in a project that I couldn't get around, I tended to find other things to occupy my hands while thinking about how I could get back to work on the other project, with the least added effort and expense. Quite often it's lack of an expensive part of material that holds me up. Whatever the reason that one, or two, or three projects are on hold, I need something to occupy my time.

Another reason for having multiple projects is simply that some of them are inter-related. I need a good working vacuum system (among other things) for several other, larger, experiments I'd like to do. The micro-Marx pulser is needed to trigger the experimental gas switch I've completed, but have not yet tested.

And while I have had a life-long tendency to take too long to finish projects, I am in fact finishing projects now that I am on the Ritalin. I have more perseverance and much more focus than ever I ever enjoyed before.

Unfortunately, having my job yanked out from under me due to a reorganization left me unable to pay for materials and parts. I also need to spend time looking for work AND trying to identify and reach my own customers for work that I can do with my own resources.

And finally, health problems of one sort or another continue to interfere with my ability to get things done.

All that said, more progress has been made on my various "mad science" / research / hobby projects in the last year than in the previous ten.

I've also been posting videos occasionally to my YouTube channel, which is HERE.

Friday, December 7, 2012

Mock-up of MLTC power box front panel

...or something close to this, anyhow. I am short on good switches & panel lamps.

Only one of those meters is suitable, I'm still looking for another. Several parts aren't really installed yet cuz I'm still making holes in the panel.

I no longer have any idea about an estimated completion date. I can do tune-up runs without meters (tho I'd rather not) but I still have to wire everything when all parts are found and installed.

Furthermore, I'm stalled again on the HV section because of a fit problem, until I can find some shorter ceramic standoffs (that I can afford).

After THAT, I still have to finish the safety gap compartment and power inlets and outlets. Oh yeah: don't have most of that hardware yet either.

There's an event in Jan. I might want to debut the coil at, assuming I can finish in December, assuming a large coil is even welcome there - I've not yet inquired. It's starting to look unlikely I'll finish in time in any case.


Wednesday, November 21, 2012

short update on Tesla coil

Haven't had much time or money for my science projects lately, but I am making plodding progress on the Tesla coil. The only remaining work is on the power panel (which, unusually, includes the HV transformer and its protection devices) and the enclosure for the primary cap.

Two additional spark gap designs are planned, but only one of the three has been finished.

"First Light" (ie, the first power-on tests and tuning) should occur some time before Christmas.

Here's a short video showing some parts I finished recently:

http://www.youtube.com/watch?v=MNoBmwaZFaQ

Friday, November 2, 2012

new web site(s) & domain & business

As I've had more and more inquiries about me doing independent (read: self-employed) technical work of various sorts (REALLY various) it's become clear I need more of a business identity, probably more than one. Some things I do don't mix well with each other, or rather, the customer bases might not.

So at least one new web site will soon be up at my shiny new domain, bill-lemieux.com

Watch this space, but be patient. The last time I made a web site, web sites were new, and I did it the old fashioned way, editing HTML by hand in a text editor, the way Tim intended, up hill, both ways!

So it will be a day or three, at least. My web-mustering skills are so musty and dusty as to be effectively non-existent for use in today's web. style-sheets? FRAMES??

Wednesday, October 10, 2012

new video - rebuilding variable transformers

I use variable transformers* a fair amount, most often in crude high voltage power supplies, such as Tesla coil power supplies. They are expensive to buy new, so I am always on the lookout for good deals on used units. Often, an old variac will have defects from abuse and will need a bit of TLC before they can be put back into service.

The item in this video was one such. It had been left sitting in a single position for many years, while more current than it was rated for ran through it. This resulted in one area of the (brass) slip ring being badly eroded and pitted, the (copper-graphite) slip ring brush being badly pitted and eroded, and some of the winding contact areas being pitted.



The (graphite) winding brush was in good shape thankfully, as it would have been a bear to replace. This first video shows how I turned down the surface of the slip ring to remove the pitted areas. The slip ring is mounted on the underside of the rotating brush plate, so you can't get a good idea of its condition unless you take the variac apart. Before you buy an old, used variac, it would be a very good idea to examine its brushes, its windings, and its slip ring carefully. If you didn't do it before you bought it, you would be smart to do it afterward before you use it, to avoid unpleasant surprises. Even if you don't own a lathe, you can do a lot of good to the slip ring with steel wool or a Scotch-Brite pad. If you decide to clean up the contact area of the windings, beware that these are often plated with a thin layer of brass to increase wear resistance vs. bare copper. If at all possible, you want to leave as much of that brass plating on the windings as possible, to extent the life of the unit. Frankly, for occasional amateur / home use, you probably won't put enough wear on those windings for it to matter, but there's no sense wasting good workmanship if you can avoid it. Not all variacs have this feature, some just provide a bare copper surface.

_____
* commonly called "variacs" by old timers - Variac™ was a trademark of the now-defunct General Radio Corporation. Other common brand names include PowerStat™ from Superior Electric and Staco, both of which are still making and selling excellent products. Finally, there is an importer of Chinese variable transformers who is using -- legally or not -- the name "Variac" in their company and domain names. Whether or not that company bought the trademarked brand from Teradyne (the inheritors of the Variac brand) I neither know nor care, because I have examined the build quality, wire size, and so forth of their units, and they do not seem worth the pricetag. Caveat Emptor!